A simple method for purifying undenatured miraculin from transgenic tomato fruit

The sweet taste-modifying protein miraculin has been successfully expressed in the tomato, a high-yield commercial plant (Sun et al. 2007). Previously proposed methods of purifying untagged miraculin from transgenic tomato fruit are laborious and time consuming and do not allow the separation of undenatured and denatured miraculin. Therefore, it is necessary to develop an efficient method of purifying undenatured miraculin from transgenic tomato fruit. In this study, we have demonstrated that the combined use of nickel-immobilized affinity chromatography and ion-exchange chromatography readily provides highly purified undenatured miraculin, as demonstrated by the observation of both a single peak from reverse phase high performance liquid chromatography and a single band from SDS-PAGE.